The present invention relates to lead shape measurement apparatus which are used in the measurement of shapes of the various types of external leads such as J-shaped external leads and curved external leads provided with crank shapes for QFP (a quadrivial-leads flat package which means flat packages with leads in four directions) and the like, and more particularly, relates to lead shape measurement apparatus which are used for the non-contact accurate measurement through image recognition of curved shapes across large areas from the vicinity of the root of an external lead to the distal end.
Conventionally, there have been apparatus which measure curves in the horizontal direction, lengths and curves in the vertical direction of external leads in semiconductor packages. The results of these measurements were then used to determine whether the product clears quality management standards for the products. Such results were also used in the adjustment of apparatus. For example, external leads have press processes executed so that they are made into the required shapes and the measurements are used to adjust the pressure, stroke and other parameters for the press, as well as for adjustment of the shape and contact status of molds.
Such lead shape measurement apparatus have included apparatus for measurement through recognition of an arbitrary positioning of a semiconductor package, such as the positions of a distal end of an external lead in the horizontal plane for example.
FIG. 1 shows one example of an apparatus which performs measurement of semiconductor package external leads which are curved in a crank shape in the horizontal plane.
In this figure, the numeral 1 is a semiconductor package to be measured, 1a is an external lead, and 2 and 3 are television cameras which are placed horizontally to the package 1 and which photograph the external leads 1a, 1a. One television camera 2 photographs a horizontal image of the external leads 1a, 1a from above, and the television camera 3 photographs a frontal elevation image of the external leads 1a, 1a of the package 1 from the side.
The numeral 4 is an image plane for the television camera 2, and the numerals 41a, 41a, . . . indicate the external leads 1a,1a in the image plane 4. As can be seen from the image plane 4, the image information from the television camera 2 enables measurement of the length and the curvature in the horizontal direction and which is called skew, for the external leads 1a, 1a.
The numeral 5 is an image plane of a television camera 3 and the numerals 51a, 51a, . . . indicate the external leads 1a, 1a in the image plane 5. In the same manner, as can be seen from the image plane 5, the image information from the television camera 3 enables measurement of the rise and fall in the vertical direction, for the external leads 1a, 1a.
The numeral 6 is an image processing apparatus and calculates the length and the curvature in the horizontal direction, and the rise and fall in the vertical direction on the basis of the image information from the television cameras 2, 3 from the respective image planes 4, 5.
However, what can be measured by this apparatus ultimately returns to the three-dimensional positions of the distal end portions of all of the external leads. This is to say that it is possible to measure only one quantity for the entire shape of the external leads, and for example, it is not possible to measure the entire shape of a radius of curvature of a curve, or the angle of each side of an external lead which is bent in a crank shape.
Because of this, an apparatus having the configuration shown in FIG. 2 has been proposed and is in practical use.
In this figure, the numeral 7 denotes a television camera 7, and a package 1 is placed horizontally, and an image of the external lead 1a when seen from the side of the package 1 is photographed by the television camera 7. The numeral 8 denotes that image plane, and the numeral 81a denotes the image of the external lead 1a inside that image plane 8, while the numeral 9 denotes an image processing apparatus 9 which calculates the related quantities on the basis of the image information shown in the image plane 8. As can be seen from the image plane 8, depending upon the image information from the television camera 7, it is possible to measure the entire shape of a radius of curvature of a curve, or the angle of each side of an external lead 1a.
However, in the case of this apparatus, there is the disadvantage that for all of the external leads 1a, 1a, it is only possible to measure the position of the frontmost portion with respect to the television camera 7, and it is not possible to have measurement for all portions.
Moreover, in the case when it is necessary to know the shape of all leads, this conventionally involved much trouble, and required inefficient work such as making measurements for one lead, and that external lead 1a being cut off after measurement and measurement being performed for the external lead 1a which was then positioned at the front.